The most common tool for dental hygiene is the toothbrush where mechanical action of the toothbrush bristles aids in the removal of food particles, plaque and stains. The toothbrush is normally used with a toothpaste which in early years consisted of a surfactant and an abrasive material intended to augment the mechanical action of the brushing.
Various active ingredients have been incorporated into toothpaste such as fluoride, tartar control agents and peroxide to provide further dental hygiene and oral care benefits. As people's interest in whitening teeth has increased, various versions of toothpaste having tooth whitening properties have become commercially available. Even though the toothpaste contains a tooth whitening agent, it is hard to achieve a significant whitening effect in a short period of time by brushing teeth for 1 to, 3 minutes of contact time between teeth and toothpaste.
Consumers have turned their attention to the cosmetic aspects of dental care, such as tooth whitening. One expensive consumer option is professional tooth whitening programs provided by dentists. They generally consist of an in-office bleaching procedure or an outside-the-office bleaching procedure. The in-office procedure involves several visits, each of which begins with the fabrication of a specially fitted rubber dam within the mouth to prevent the whitening chemicals that have bleaching action, typically hydrogen peroxide, from contacting the soft oral tissue. The production of the rubber dam within the patient's mouth may be both uncomfortable and time consuming. The strength of the peroxide bleach mandates the use of the dam. The in-office procedure may also leave the teeth sensitive to heat and cold and is very expensive.
The outside-the-office whitening program differs in that the patient applies the bleaching agent to his or her own teeth using a lower strength chemical bleaching agent over an extended period of time, typically several hours a day for several weeks. The outside-the-office program typically requires an initial fitting in the dentist's office for a device which is specific to the particular patient. The device is fabricated to fit precisely onto the patient's teeth and is used to deliver a bleaching product to the patient's teeth such as a gel containing a hydrogen peroxide complex. The patient is responsible for measuring and applying the bleaching agent to the surfaces of the teeth using the device as the means for delivery and containment. The reusable device must be durable to endure repeated handling, cleaning, filling, installation, and wearing. The device is typically rigid in order to maintain fit during repeat use and in many cases can cause discomfort and gum irritation.
There are now non-professional programs available to persons interested in whitening their teeth using commercial products available at drug stores. The commercial products provide a kit which includes a generic appliance and a container of bleaching gel. The obvious appeal is the lower cost of the program. A major disadvantage of this “one size fits all” appliance is the greater void between the interior walls of the appliance and the teeth versus the professionally fitted appliance. In order to insure intimate contact of the bleaching gel and the teeth surfaces, more bleaching gel is required. Furthermore, the poor fit means a greater loss of bleaching gel onto the gums, into the oral cavity, and eventual ingestion. The commercial kits, like the outside-the-office professionally administered program, require the user to clean and to reuse the appliance. Since generic appliances are not fitted to the individual user, they are even more bulky in the mouth than the fitted appliances and thus they restrict social discourse to a greater degree.
One attempt to remedy some of the problems of the commercial kits is disclosed in U.S. Pat. No. 5,575,654, issued to Fontenot on Nov. 19, 1996. Fontenot discloses a prepackaged moldable dental appliance, adapted to fit a wide range of variously sized dental arches, which contains a premeasured amount of medicinal or bleaching agent. In use, the dental appliance is removed from the packaging, aligned in a parallel fashion to the edges of the teeth and pushed over the teeth in the direction of the periodontal tissue until it covers the teeth surfaces. The primary benefit of the device disclosed by Fontenot is elimination of the measuring and filling of the appliance and the disposability after each use.
Japanese Patent No. 12-281,548, filed on Mar. 16, 1999 and published on May 30, 2000, discloses a tooth whitening kit set utilizing devices such as water-insoluble tape, sheet, film, dental tray, mouth tray, mouthpiece, impression pack, pack material, and chewing brushing having a plurality of protrusions on a surface contacting with the teeth. The invention requires thinly applying a whitening component in a wet gel phase to a supporting layer of the above devices or by immersing the adhesion portion of the above devices in a solution containing a whitening agent which means the devices claimed in this patent are wet type. When using devices like this, it is unduly cumbersome and the whitening agent can contact the hands or other body parts causing irritation.
U.S. Pat. Nos. 5,310,563 and 5,639,445, assigned to Colgate-Palmolive company, disclose a dental material comprising an active component dispersed in a polysiloxane polymer composition sold by Dow Corning Corporation under the trade name Dow Corning 3179 Dilatant Compound which is attached to the teeth by pressing it against the teeth and the gum. It is easily removed from the teeth without breaking into pieces and adhering to tooth surfaces. The material has the active component encapsulated in the polymer whereby the active component cannot be easily released necessitating extended contact time in order to obtain a tooth whitening effect.
U.S. Pat. Nos. 5,879,691, 5,891,453 and 5,989,569 assigned to Procter & Gamble disclose a delivery system for a tooth whitener, comprising a transparent, thin and flexible polyethylene strip having a professional whitening gel and the like thereon, wherein the professional whitening gel is pre-coated in a manufacturing process or applied directly by the wearer before attaching the strip to teeth. Since it does not use a mouth tray, user friendliness is improved but it is still a wet gel system that requires special handling and precaution. The strip is thin and transparent so daily life is not interrupted when wearing the strip. Reviewing the examples, the invention of these patents is considered a wet type liquid tooth-whitening system constructed by using a tooth whitening substance along with a synthetic gelling agent, preferably carboxypolymethylene, obtained from B.F. Goodrich Company under trade name of Carbopol to form a liquid gel along with water, pH adjusting agent and carrier materials which is then applied wet onto a strip of flexible material. When handling this type of system or attaching and wearing the system on the teeth, the gel containing peroxide at a high concentration as a tooth whitener may transfer and adhere to the hands, tongue, gum and the like. Therefore, there is room for improvement in handling and application.
U.S. Pat. Nos. 6,682,721 and 6,780,401 assigned to LG Household And Healthcare Ltd. disclose a dry type patch for tooth whitening that overcomes the limitations and undesirable handling and safety characteristics of the wet gel methods noted above. Unfortunately, while the dry type strip is consumer friendly in terms of safety, application and use, the product uses costly ingredients applied at low solids that raise the cost of manufacturing. The dry LG product has less of a market share than the wet gel systems because of the cost of manufacturing. This is because the patented formulation comprises expensive raw material synthetic-polymers and a multi-step coating process for the active layer and the backing layer that is very costly. While this dry strip is a better product design than the wet system of Proctor & Gamble because it is easier to use and will be preferred by the consumer, manufacturing cost and market economics appear to have kept LG, a worldwide consumer products giant from penetrating the U.S. and European markets and have limited the success of the dry strip technology to a minor almost negligible share in Asia.
The whitening strips used in the market today are divided into two categories: a wet gel type like the Proctor & Gamble product and a dry type like the LG product described above. The wet type strip is for example, a hydrogel formulation such as a high viscosity gel applied to a film backing, or a formulation formed by applying a gel to an adhesive layer or immersing an adhesive layer in a solution. This type of strip is considered wet since the content of water or ingredients in the formulation such as glycerin is high and the fluid gel will flow and transfer. This type of strip is messy because of free gel or fluid and is not preferred by the consumer. The wet formulation generally lacks strong adhesion strength and relies on high viscosity for adhesion. Since it is sticky in its initial state, when a user handles it, gel may adhere to hands when attaching the strip to the teeth. When a user fumbles about to try to attach the strip to the contours of the teeth, a gel formulation including peroxide at a high concentration may adhere to undesired areas such as hands, mucus membranes, lips, tongue, etc, causing irritation.
The dry type strip such as the LG product defined above is characterized in final form by the fact that it solid and not liquid and has low levels of retained volatiles versus the wet gel system. The dry strip is defined by not being liquid and containing less than 6% retained volatiles as packaged not including peroxide based on studies of dry strips commercially available from Asia.